DNA damage causes chromosomal instability, oncogensis, cell death, and severe dysfunction of cells. The DNA repair system is crucially important for the survival of living cells. The two major DNA repair mechanisms involved in the repair of double stranded DNA breaks are homologous recombination (HR) and non-homologous end-joining (NHEJ). The eukaryotic RAD51 gene is an ortholog of Escherichia coli RecA, and the gene product RAD51 protein plays a central role in homologous recombination.
Many therapeutic treatments, such as anti-cancer agents, exert their therapeutic effects through their capability of producing DNA damage to cells. If the cells, such as cancer cells, have active DNA repair mechanisms, the therapeutic effects of such treatments may be compromised and high dosages may be needed for achieving the desired therapeutic effects.